BayCEER Workshop 2008

Quantitative Determination of Perfluorinated Surfactants in Water

Liquid chromatography (LC) interfaced by electrospray ionisation (ESI) to tandem mass spectrometry (MS/MS) has, since its inception, proven to be a sensitive and selective approach for trace analysis of polar hydrophilic compounds in aqueous matrices. On the other hand, the advantage of high selectivity of the ESI source entails also problems, i.e. the fact that ionisation yields are largely dependent upon the sample composition in respect to accompanying substances and the concentration of analytes.
Perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS) and derivatives of the latter are widely used as specialty surfactants; they are now globally distributed and have considerable ecotoxicological risk potential due to their high persistence. The most common method for their quantitative analysis in various environmental compartments, especially the hydrosphere, involves solid phase extraction (SPE) followed by LC-ESI-MS/MS.
Two major problems must be carefully addressed in order to avoid erroneous data: 1) during SPE, contaminations from laboratory chemicals and materials containing traces of PFOA/S may contribute to high blank levels; 2) during LC-ESI-MS/MS, ionisation yields depend on the actual sample composition_. As a consequence, the major requirements for method optimisation for reliable quantitative determination are to make sure (1) that blank levels in all laboratory chemicals and on surfaces of equipment are close to nil, and (2) that calibrations are done in such way that possible fluctuations in the ESI-ionisation are corrected.
Using the optimised method, levels of PFOA/S in the river Roter Main near Bayreuth have been determined showing that waste water, even when treated, is an important source of these surfactants in the aquatic environment.